TWO NEW ATLANTIC DOG SHARKS — SPRINGER 



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jaws similar, vestigial accessory cusps present on occasional teeth but 

 most of these single; a few teeth, tricuspid in outline, in most speci- 

 mens examined. Dermal denticles of adults similar in structure over 

 the flat surfaces of the skin of the body, typical denticles regular in 

 outline, 4-ridged, with the two central ridges reaching or nearly reach- 

 ing the posterior apex, denticles usually longer than broad (one of 

 average size, 0.21 by 0.35 mm), 6-ridged denticles rare even along the 



FiGUKE S3.-Typical dermal denticles from the lateral surface of Mustelus norrisi, new species, showing 

 long ridges, reaching or nearly reaching the apex. 



middorsal line. Color uniform, without lighter or darker spots; Ught 

 gray. Measurements of the types are given in table 1. 



Comparisons with other species.— Because of differential growth, 

 especially pronounced in this family as soon as maturity is reached, 

 measurements expressed as a percentage of the total length have little 

 value for taxonomic purposes unless several factors are taken mto 



